1. Field of the Disclosure
The present invention relates in general to absorbing vibration and impacts during down hole drilling and, in particular, to a system, method and apparatus for protecting measurement while drilling devices.
2. Description of the Related Art
In the oil and gas industry, there is always a need to make down hole electronic devices more reliable. Down hole electronic devices that are used while drilling operate at high levels of both vibration and temperature. These environmental factors cause down hole electronic devices to fail at a much higher rate than surface devices. Any failure of a down hole electronic device is costly since drilling operations typically must be stopped and the down hole tools must be removed from the hole. Such operations can require a few hours to a few days, and can cost thousands or hundreds of thousands of dollars. Accordingly, any device that reduces the frequency at which down hole failures occur is desirable.
Most down hole electronic devices are operated with some means (e.g., a snubber) of isolating them from the shock and vibration that is present in a drilling situation. Devices such as snubbers provide some levels of shock and vibration protection. However, conventional devices are limited by one or more of the following constraints: their size must be relatively small, all elements of the device must be able to withstand temperatures of at least 150 degrees C., and the device must not expose the system to any additional risk (e.g., the increased movement of the device must not add to the tendency for wire harnesses break prematurely).
Measurement while drilling (MWD) devices are designed to work in conditions of high vibration and temperature, and also within a very high flow rate of an abrasive slurry called drilling mud. Because of this, every external part of the system has a finite life span. The wearing out of and replacement of these elements is a significant contributor to the material cost of operating MWD systems. Larger parts of the expensive materials needed for such operations are more costly. In order for an operator to be competitive in the marketplace, it is imperative that the MWD tools be no larger than they need to be. Moreover, many MWD operators employ systems based on an industry-standard vibration absorber or snubber. See, e.g., http://www.aps-tech.com/products/vibration/mwd-vibration-isolators.php. Thus, it is desirable for new or improved designs to fit within the size constraints imposed by that design.
The temperature requirement is significant because the majority of compliant plastic materials (polyurethane, for example) start to lose their mechanical properties at 100 degrees C. This means that some preferred means of absorbing shock and vibration are disqualified.
The need for the device to avoid introducing additional risk is fairly self-evident. The device cannot damage the functionality of the MWD system in the event that it should fail. The device must be “fail safe” such that no damaging or costly system failure occurs. Thus, continued improvements in MWD shock and vibration dampening are desirable.